The invention relates to an apparatus for the filtering and separation of flow media (raw media) enriched with foreign matter, particularly of liquid media, utilizing the principle of ultra-filtration by means of a membrane separation apparatus, wherein the flow medium is admitted to the membrane separation apparatus and is divided into a retentate enriched with the foreign matter and wherein at least the permeate is discharged by way of at least one outlet.
Such apparatus have been known for some time in various different forms. They are utilized for different separation purposes, and for different flow media to be separated, for example for gaseous flow media, vapor-like media and also for liquid media. An area of application which becomes increasingly prominent for economical as well as ecological reasons is the separation of municipal and commercial waste waters which include relatively large amounts of biological foreign matter. These flow media in the form of municipal and commercial waste water which below will simply be called waste water, pose high requirements with regard to the membrane separation devices used in the apparatus, the effectiveness of the separation of the waste water into pure water obtained as the permeate and concentrate representing the retentate with regard to a service-free long time use, a good servicing capability and an unproblematic easy exchange of membrane equipment when the membrane separation devices become inoperative that is they can no longer fulfill their purpose of separation or when they are totally destroyed.
The waste waters addressed herein include relatively large amounts of various types of foreign matter. The greater the proportion of foreign matter in a certain volume of the flow medium, the greater is also the probability that the foreign matter is deposited on the membrane separating structure and covers increasingly large areas of the membrane after first an area (cluster) of the membrane is occupied by the foreign matter until the whole active surface of the membrane element is covered and the membrane element becomes inoperative. In this connection, it is said that the membrane element is totally blocked.
The blocking of the membrane however occurs often because of the way the flow medium enriched with the foreign matter is guided through the apparatus. Often, the flow passages are complicated so that, in order to achieve a minimum flow speed for the flow medium, the flow medium must be subjected to relatively high pressures to overcome the hydraulic resistance occurring in the apparatus because of its complicated design. This also results in a relatively high energy consumption.
However, a problem of greater impact than the high energy consumption concerns the membranes utilized which need to be designed in such a way that they can withstand the high pressures in order to be able to be utilized in the present apparatus for the given purpose. State of the art apparatus utilize flat membranes of various types which are stacked in spaced relationship from one another such that the flow medium to be separated passes through the apparatus from its inlet to its outlet in a meander-like fashion while flowing along the membrane elements. A blocking of, or damage to only a single membrane element in such an arrangement means that the whole apparatus must be fully disassembled, the respective membrane element must be replaced and the apparatus must be reassembled. This requires a relatively large amount of time which results in relatively high operating costs. For waste water with relatively large amounts of waste such apparatus and membrane elements have therefore been found to be not particularly suitable.
In order to avoid a disassembly of the known apparatus, it has therefore been tried--which in many cases is still being done--to clean the apparatus by means of a separate cleaning solution which is conducted through the apparatus and which includes chemical ingredients specifically formulated for the removal of the foreign material from the membrane elements. In this way, however, the cleaning agent which includes chemical ingredients forms another mixture which must be collected separately as it cannot be simply discharged to the waste water system, but must be separately processed that is decontaminated.
It is therefore the object of the present invention to provide an apparatus of the type mentioned above which however requires only a relatively low pressure to provide for the flow of the flow medium through the apparatus and which facilitates replacement of the membrane separation structure when the separation efficiency of the flow medium becomes too low or a membrane separation structure is blocked. In addition, the apparatus should be easy to clean when the separation efficiency drops but, in any case, it should remain operative without servicing over long periods. Also, the apparatus should be usable at any location and use only relatively little energy for its operation. Finally, it should be simple in design so that it can be made and operated relatively inexpensively.